In a conventional mobile communication system using a CDMA system, FCS (Fast Cell Selection) is one of systems whereby a communication terminal apparatus selects one base station apparatus from among a plurality of base station apparatuses to communicate. According to FCS, a communication terminal apparatus compares the reception quality of known signals sent from a plurality of base station apparatuses and communicates with a base station apparatus, which has sent a known signal of the best reception quality.
For example, when a communication terminal apparatus changes a base station with which to communicate by measuring the reception quality of known signals and selecting a base station apparatus which has sent a known signal of the highest quality, the communication terminal apparatus formally sends a connection request to the base station apparatus which has sent a known signal of the highest reception quality.
Then, the base station apparatus decides radio resource assignment and a communication method from the reception quality information of the known signal sent from the communication terminal apparatus and enters into communication with the communication terminal apparatus. The communication method here refers to settings of signals to be sent by the base station apparatus such as a modulation scheme of signals to be sent, coding rate, spreading factor in a CDMA communication and number of multicodes.
However, in the case of a conventional apparatus, a communication terminal apparatus sends reception quality information of a known signal sent from a base station apparatus, which is the communication partner, to this base station apparatus, whereas the communication terminal apparatus does not send reception quality information of known signals sent from base station apparatuses with which it is not communicating to these base station apparatuses. Then, when the communication terminal apparatus changes the base station apparatus with which to communicate, the communication terminal apparatus sends the reception quality of a known signal of a base station apparatus with which the communication terminal apparatus desires to have a new communication to this base station apparatus.
In a conventional apparatus, when there are variations in a propagation path due to fast fading, etc., even if the communication terminal apparatus measures reception quality information of a known signal and sends the information, the situation of the propagation path is likely to have changed drastically when the base station apparatus uses the information and the base station decides radio resource assignment and a communication method based on the reception quality information and may fail to set sufficient conditions to carry out a communication, causing the communication terminal apparatus to fail to correctly receive a signal sent by the base station apparatus immediately after the transmission.